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High Precision Event Timer (HPET)
The HPET is a timer chip that in some future time is expected to completely replace the PIT. It provides a number of hardware timers that can be exploited by the kernel. Basically the chip includes up to eight 32 bit or 64 bit independent counters. Each counter is driven by its own clock signal, whose frequency must be at least 10 MHz; therefore the counter is increased at least once in 100 nanoseconds. Any counter is associated with at most 32 timers, each of which composed by a comparator and a match register. The HPET registers allow the kernel to read and write the values of the counters and of the match registers, to program one-shot interrupts, and to enable or disable periodic interrupts on the timers that support them.